1. The Senses
Stimulus: form of Energy
Sensory Receptors: - convert one source of E into another
- modified ends of sensory neurons
- amplifies E of stimulus to ensure it reaches threshold levels
Taste: Chemical Stimulus
taste buds detect presence of chemicals
Smell: Chemical
olfactory cells detect presence of chemicals
Pressure: Mechanical Stimulus
movement of skin, changes in body temperature
Proprioceptor: Mechanical
movement of limbs
Balance: Mechanical
body movement
Audio: Sound Stimulus
sound waves
Visual: Light Stimulus
changes in light, intensity, movement, colour
Thermoreceptor: Temperature Change stimulus
flow of heat
-Still, much of environment remains undetected
- Each mechanoreceptor a modified dendrite of sensory neuron
Sensory adaptation
- Occurs once receptor becomes accustomed to stimulus
Neuron ceases to fire even with present stimulus
Protected by epidermis, dermis
Taste receptors
- Different locations in different species (usually in long skinny part at top or bottom) except
humans
- Action potential increases with sugar present
- Once dissolved, taste buds stimulated into taste (sweet, salty, sour, bitter)
Olfactory Cells (Smell)
- In nasal cavity
- Airborne chemicals combine with receptor ends on olfactory cells to create ap
- Impulse from this carried to frontal lobe (reduced by clogged nasals)

2. -Demonstrate sensory annotation (adjustment)
Nerve impulse in frontal lobe creates sensation, this becomes perception
-Determined by unique perceptions (unique understandings of things)
The Eye
- Composed of 3 layers:
- Sclera: white fibrous outermost layer
protective layer, maintains eye shape
Front is covered by cornea: - transparent
- no blood vessels
- requires O2 (gases dissolved in tears), nutrients (aqueous humour)
- chamber of trans. fluid behind cornea
- Choroid Layer: middle layer
contains blood vessels
- pigment granules prevent light into eye from scattering
- front of this layer is iris: - thin circle muscle controls size of opening
- behind retina is lens: - focuses image on retina
ciliary muscles: alters shape of lens
- behind lens is vitreous humour: cloudy, jelly like
- maintains shape of eye, light transmission
- Retina: innermost layer
composed of light-sensitive cells, bipolar cells, optic nerve cells
-2 types of light-sensitive cells:
Rods: low-intensity light (grey, black, white)
extremely sensitive
concentrated in outer edges
Cones: high-intensity light (colour)
not sensitive, requires intense light
focuses light onto fovea to produce image
concentrated in fovea (back, centre of retina)
needed for high acuity tasks (ie reading)
-3 types of cones, each in range of colour
-Lack of cones > colour blindness
Fovea Centralis: -depression in centre of retina
-most sensitive area, contains packed cones surrounded by rods
-most light rays fall here, explains why colour needed to see object from periphery vision
-No rods or cones in area where optic nerve, retina come in contact
- Blind Spot
-not noticed because info in occipital lobe carries info to both visual tracts
-Leads to...

3. bipolar cells >>> these cells are middle layer and stop releasing inhibitory transmitter into
synapse when liht stimulates rods, cones
ganglion cells >>>> action potential from bipolar cells come here, form optic nerve (close to
vitreous humour)
Light goes from cornea>lens>fovea
Summary:
Sclera: supports, protects photocells
Cornea: refracts light to pupil
Aqueous Humour: supplies cornea with nutrients, helps refract light
Choroid Layer: contains blood vessels nourishing retina
Iris: regulates light to eye
Vitreous Humour: maintains eyeball shape, permits light to retina
Lens: focuses image on retina
Pupil: opening in iris allows light to eye
Retina: rods for dim light, cones for colour
Fovea Centralis: most light-sensitive area of retina, only cones
Blind Spot: optic nerve attaching to retina with no rods/cones
Focusing:
Light passes thru rigid cornea, flexible lens, fluid humours
Image projected, then fixed upon fovea is smaller, upside down, reversed left to right
-Lens flexible, can change shape for focusing (accommodation)
-Object Far Away: Ciliary muscles relax, suspensory ligaments tighten, lens flattens
-Pupil dilates
-Object Close Up: Ciliary muscles contract, suspensory ligaments relax, lens roundens
-Pupil constricts
Conditions:
-Older lens, protein structure degenerates, making it opaque and less light passing thru
-Cataracts: causes grey-white spots, lens becomes opaque
strong eyeglasses, plastic lens needed
-Inherited conditions: -Astigmatism: uneven curvature of part of cornea
-Vision defects: -Glaucoma: increased buildup of aqueous humour
-ducts drain excess fluid, blockage here causes fluid pressure to collapse
retina blood vessels
-as result, less nutrients, o2, neurons die and blindness results
-Myopia (Nearsighted): -focus on close objects, not far ones
-elongated eyeball, image in front of retina

4. -concave lenses needed (diverge light)
-Hyperopia (Farsighted): -focus on far, not close ones
-short eyeball, image in back of retina because lights dont meet
-convex lenses needed (light at sharper angle)
-Light received to photoreceptors (rods,cones) becomes vision
-Each neuron has different view >>>> brain, all these processed into cerebrum (occipital lobe)
as image
-Cerebrum takes info to both eye tracts
Binocular Vision: Allows brain to perceive depth perception, 3D